Photomechanical copy method



May 13, 1952 UNHA RDE NE D EMULSION LA YER F/XED AND WAS/IEOPHOTOGRAPH/C ELEMENT RECE/ V/NG JUPPOR T TRAMSFfRR/NG A STRATUM 0FEMULSION w TRANSFER/WED EMULSION 577M TUM EDWARD C YA CKEL INVENTOR m2BY ATTORNEYS Patented May 13, 1952 UNITED STATES g'rsnr orricsPHOTOMECHANICAL COPY METHOD Application November 4, 1947, Serial No.783,913

Claims.

This: invention relates to photography and more particularly toaphotomechanical copy method for use-in the reproduction of printedmatter.

There are a number of well-known photographic'methods'of reproducingdesigns such as printed matter on paper or other supports. For instance,by the so-called reflex copy method an emulsio'n'layer isexposed'through its support and the printed matter is-reproduced asanegative. Or one may print a negative and a positive therefrom byconventional methods. In the photomechanical art a common practice is toexpose a suitable photographic element such as a tissue and to transferthe exposed element to a metal plate after which the unexposed emulsionis washed off the plate or the washing off may occur before transfer ofthe resist to the plate. However, none of these processes possesses thefeature of transferring a thin stratum of a photographic image to asupport or a method of making a multi plicity of prints by transferringa plurality of strata from a photographic emulsion layer. I havesucceeded-in perfecting a method of doing this which, in general,consists of preparing a photographic image in a substantiallyunhardene'd layer of colloid vehicle and transferringacontinuousstra-tum of the entire layer to a support;

One object of my invention is to provide a simple" photographic processof reproducing a subject such as printed matter in the mannerabove-mentioned. Another object is to provide tliem'a'teri'als andphotographicand mechanical processes and variations of the same, towhich my invention issusceptible; Other objects will become'apparentfrom the following description of my invention.

According to the broader aspects of my invention a substantiallyunhardened light-sensitive photographic emulsion layer, such as ag'elatino-silver halide emulsion layer, is exposed toa subject andsubsequently at some stage in the processing cyclea thin continuousstratum of the entire layer is transferred to a support.

My'inventi'on will be'better understood by refer'ence to theaccompanying drawings wherein Fig. 1 shows in enlarged cross-sectionalView the appearance of' a processed photographic element carrying anunhardened emulsion layer containing a silver image.

Fig. 2 shows in enlarged cross-sectional view the method of transferringa stratum of the processed emulsion layerto a receiving support.

Fig. 3 shows in enlarged cross-sectional view 2 the appearance of thetransferred emulsio stratum on the receiving .support. I

My invention will now be described in greater detail with reference tothe accompanying drawings.

According to the preferred embodimentofmy invention, I take asubstantially unhardened light-sensitive silver. salt emulsion layer,such as a gelatino-silver halide emulsion layer; containing little or nohardening agent coated on a suitable support as paper, filin, or othermaterial, and expose by projection or' contact printingto a negative soas to obtain a reverse position,- after which the exposed photographicelement is developed in an ordinary black-and- White developer, fixed ina non-hardening fixing bath, and then Washed. After washing, when theemulsion layer is still moist, I rolldown a suitable receiving support,such aspaper, cloth, wood, or similarabsorptive'material, onto theemulsion layer, and, after stripping the receiving support-from theemulsion layer, a thin stratum of emulsion is found transferred to thereceiving support; The appearance of the fixed-and-washed photographicelement is shown in enlarged cross-sectional view in Fig. 1 whereinlayer In is the emulsion support of a proper base carrying theunhardened emulsion layer ll containing the silver image I2. The methodof transferring a stratum of the emulsion layer of Fig. 1 to a receivingsupport is shown in enlarged cross-sectional view in Fig; 2 whereinlayer l'fl-is the emulsion support carrying the residual unhardenedemulsion layer [3' andresidual'silver image Mwhich are left on supportl0 after stripping off the stratum of emulsion l5 containing the stratumof image H on the receiving support IS. The appearance of thetransferred emulsion stratum on the receiving support is shown inenlarged cross-sectional view in Fig. 3 wherein layer I6 is thereceiving support carrying the emulsion stratum I5 containing the imagestratum H.

The above-described process is similar to that disclosed and claimed inthe Yutzy and Yackel, UL S. patent application Serial No. 783,914 filedconcurrently herewith. However, the present process differs in therespect that in my process a continuous stratum of the entire emulsionlayer is transferred to a receiving support whereas in the co-pendingprocess a stratum of only the unhardened image area ofa differentiallytanned emulsion layer is transferred to a support.

The following examples are illustrative of my invention but are to beconsidered as in no way limiting the scope of my invention.

Example 1 An emulsion suitable for use in my process can be made bypreparing solutions of (A) 25 grams of gelatin in 1 liter of water at 40C., (B) 100 grams silver nitrate in 500 cc. water at 20 C. and (C) 35grams of sodium chloride in 500 cc. of water. Solutions B and C aresimultaneously run into solution A at a uniform rate while stirring thelatter, over a period of about ten minutes; solution B preferably notbeing allowed to run in faster than C. Thereafter 400 grams of gelatinin 4 liters of water at 40 C. are added. Preparatory to coating anemulsion layer, 2 cc. of 10 per cent formaldehyde solution may be addedto the emulsion providing that a gelatin of poor physical properties hasbeen used, and this composition is then coated on a support such aspaper containing no agent tending to further harden the emulsion. Afterdrying, the product is ready for use. The amount of hardening agentadded to the emulsion layer depends somewhat upon the characteristics ofthe particular type of gelatin in use and in general it is unnecessaryto use a hardening agent. When a hardener is used, ordinarily it is notnecessary to use more of a hardening agent such as formaldehyde than theamount specified. If another hardening agent such as chromium salts oralum is used, due regard is given to differences in hardening activity.The emulsion layer is then exposed to a suitable negative as statedabove using suitable light intensity and time of exposure. Followingexposure the element is developed in an ordinary black-and-whitedeveloper such as one having the following composition:

Water (50 C.) cc 500 p-Methylamino-phenol sulfate gms 3.1 Sodium sulfite(dry) gms 45.0 Hydroquinone gms 12.0 Sodium carbonate (dry) gms 67.5Potassium bromide gms 1.9 Water to liter 1.0

For use the above formula may be diluted 1 to 4 times, depending on theresults desired.

After developing the emulsion layer it is then fixed-out in a fixingbath of the following composition:

Water, about 125 F cc 500.0 Sodium thiosulfate gms 240.0 Sodium sulfite(dry) gms 10.0 Sodium bisulfite gms 25.0 Cold water to liter 1.0

After washing the fixed photographic emulsion well, I may treat theproduct with a 5-20 per cent solution of urea or one of the gelatinsoftening solutions shown in the following table:

Percent Formamide 2-20 Ethylene chlorohydrin 5-20 Sodium nitrate 5-20Glycerol -20 the image on the receiving support. In order to makesucceeding prints the emulsion layer residing on the original support ismerely moistened again with the solution, for example, of urea or one ofthe materials above mentioned. Following this the transfer is made to anabsorbing support as before.

Example 2 In a manner similar to that of Example 1, the transfer may bemade from the washed emulsion layer by placing the emulsion layer incontact with a receiving support having its temperature raised highenough to cause the surface of the emulsion layer to melt and effecttransfer of a melted stratum to the heated receiving support. Thetemperature'selected, of course, is dependent upon the hardness of theemulsion layer, and in certain cases it may be desirable to use atreatment with one of the gelatin-softening solutions above, as well asraising the temperature at which the transfer is made. Successivetransfer prints are made by a similar treatment which softens a stratumof the emulsion layer to the desired extent. Naturally, the depth towhich the emulsion layer is softened determines the thickness of thetransferred stratum.

A number of variations may be made in my process, as will be apparentfrom consideration of the data in the following table.

processing.

Process No. 5 (Example 1) is the preferred embodiment of my inventionprincipally because of the fewer number of steps required to obtain anoptimum number of finished prints. It is apparent that the purpose of myprocess is to make multiple prints. Ten or 12 prints may be obtained. Imay make a number of prints in the manner described, for example, inprocess No. 5 above, and after the desired number of prints, as 3 to 5,have been made, I may dry the residual emulsion layer on its support andstore it away for future use. At a later date I may then resoften thematerial using water or a solution of one of the softening agents abovementioned, and after this make more prints in like manner. In theprocesses Nos. 1-5, when I apply a solution for softening a stratum ofemulsion layer, this solution is applied previous to making thetransfer.

A number of advantages of my process over prior art processes for themultiple reproduction of images are now apparent. My process possessesall of the well-known advantages of silver salt emulsion layers overprior art sensitive materials, such as glue-bichromate layers. Also, myprocess provides a quick and cheap reproduction method of particular usein the photomechanical art. Furthermore, my process is capable of a widerange of variation both in method of operation and the materials used.

My invention is subject to a number of variations. The vehicle in whichthe light-sensitive silver salt such as silver halide is dispersed, maybe composed of any of a number of substances such as gelatin, polyvinylalcohol, partially hydrolyzedcellulose esters, partially hydrolyzedpolyvinyl esters, and other resins such as polyacrylamide. In-fact, itis only necessary to select an emulsion vehicle which can be swollen bythe processing solutions to the extent that the vehicle will adhere toor be absorbed by the receiving support. The silver salt dispersed inthe emulsion vehicle is not critical since it may be any of thewell-known types such as silver bromide, silver chloride, or silveriodide, or mixtures thereof.

Without departing from the spirit of my invention, an image may beformed in unhardened colloid vehicle by means other than by exposure ofa silver salt and subsequent processing thereof. For example, I may forma colored image in the layer as by imbibition and make successivetransfers of continuous strata of this layer to receiving support.Similarly, the image in the layer may be formed by means of thewell-known toning methods. The principal feature of my process lies inthe ability to transfer an image from a soft emulsion layer, no matterwhat method was used for forming it therein, in the form of a continuousthin stratum, to a receiving support.

Process No. 3 shown in the above table represents a process almost asvaluable as the preferred process No. 5. According to this process I canput the agent used for softening the emulsion vehicle into the developersolution and make useful transfers without further treatment. Thesetransfers will have fairly good stability, however, not of archivequality, because the silver halide will print out and some subsequentdevelopment will occur tending to darken the highlights and lower thecontrast of the image.

It is necessary for the successful operation of the invention that theemulsion layer not be harder than would be the case with gelatincontaining 0.25 ounce of formaldehyde (40 per cent diluted 1:3 withwater) or 0.7 gm. dry formaldehyde per pound, when freshly coated, or0.1 ounce of the solution per pound for a sample aged three to sixmonths. By substantially unhardened as used herein, and in the appendedclaims, it is to be understood that this means a hardness for theemulsion layer of the order obtained with gelatin treated withformaldehyde under the conditions above. Strata of emulsion layersappreciably harder will not transfer satisfactorily.

The expression transferring a continuous stratum of the entire emulsionlayer, as used here and in the appended claims, is defined as the meansin my process whereby a thin layer of the total surface of thephotographic element is carried off onto a receiving support. It doesnot contemplate transferring just a portion of the surface as in theabove-mentioned invention of which I am joint-inventor.

The invention having been described, I would have it understood that thedisclosure herein is by Way of example, and included in the inventionare all modifications and equivalents falling within the scope of theappended claims.

What I claim is:

1. A method of photographic reproduction which comprises exposing asubstantially unhardened light-sensitive gelatino-silver halide emulsionlayer to a subject, said layer being not harder than a gelatin layercontaining 0.7 gram of formaldehyde per pound of gelatin freshly coated,developing in said emulsion layer in substantially unhardened gelatinvehicle an image corresponding to said subject, pressing an ab- .6scrbent support against said" layer while said layer is moist to causesaid layer to adhere to the support and without drying separating saidsupport and layer to transfer a continuous stratum of'the entire layerto saidsupport.

2. A method of photographic reproduction which comprises exposing alight-sensitive substantially unhardened gelatino silver halidephotographic emulsion-layer to a subject, said layer being not harderthan a gelatin layer containing 0.7 gram of formaldehyde per pound ofgelatin freshly coated, developing in said emulsion layer insubstantially unhardened gelatin, an image corresponding to saidsubject, pressing an absorbent support against said layer while saidlayer is moist and free of greasy material to cause said layer to adhereto the support, without drying separating said support and layer totransfer a continuous stratum of the entire layer to said support,rewetting said emulsion layerand transferring another stratum of theentire emulsion layer to an absorbent support.

3. A method of photographic reproduction which comprises exposing alight-sensitive photographic gelatino-silver halide emulsion layer to asubject, said layer being not harder than a gelatin layer containing 0.7gram of formaldehyde per pound of gelatin freshly coated, developing insaid emulsion layer in substantially unhardened gelatin an imagecorresponding to said subject, fixing and washing the developed emulsionlayer without hardening it, pressing an absorbent support against saidlayer while said layer is moist and free of greasy material to causesaid layer to adhere to the support and without drying separating saidsupport and layer to transfer a continuous stratum of the entire layerto said support.

4. A method of photographic reproduction which comprises exposing alight-sensitive photographic gelatino-silver halide emulsion layer to asubject, developing in said emulsion layer in substantially unhardenedgelatin an image corresponding to said subject, said layer being notharder than a gelatin layer containing 0.7 gram of formaldehyde perpound of gelatin freshly coated, fixing and washing the developedemulsion layer without hardening it, pressing an absorbent supportagainst said layer while said layer is moist and free of greasy materialto cause said layer to adhere to the support and without dryingseparating said support and layer to transfer a continuous stratum ofthe entire layer to said support, moistening the remaining emulsionlayer and transferring another continuous stratum of said emulsion layerto an absorbent support.

5. A method of photographic reproduction which comprises exposing alight-sensitive substantially unhardened gelatino-silver halide emulsionlayer to a subject, said layer being not harder than a gelatin layercontaining 0.7 gram of formaldehyde per pound of gelatin freshly coated,developing in said emulsion layer in substantially unhardened gelatin animage corresponding to said subject, treating said emulsion layer with agelatin softening agent, pressing an absorbent support against saidlayer while said layer is moist to cause said layer to adhere to thesupport and without drying separating said support and layer to transfera continuous stratum of the entire layer to said support.

EDWARD C. YACKEL.

(References on following page) REFERENCES CITED Number The followingreferences are of record in the 1944'123 file of this patent: 2,367,939

UNITED STATES PATENTS Number Name Date Re. 20,694 Miller Apr. 12, 1938Number 116,720 Loemmel July 4, 1371 168,578 663,539 Giesecke Dec. 11,1900 226,598 1,567,333 scharschawsky Dec.29,1925 10 231,413 1,793,070Eldridge Feb. 17, 1931 324,330

Name Date Fleishmann et a1. J an. 16, 1934 Gregory Jan. 23, 1945 FOREIGNPATENTS Country Date Great Britian June 1, 1922 Great Britain Dec. 22,1924 Great Britain Apr. 30, 1926 Great Britain J an. 13, 1930

1. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES EXPOSING ASUBSTANTIALLY UNHARDENED LIGHT-SENSITIVE GELATINO-SILVER HALIDE EMULSIONLAYER TO A SUBJECT, SAID LAYER BEING NOT HARDER THAN A GELATIN LAYERCONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED,DEVELOPING IN SAID EMULSION LAYER IN SUBSTANTIALLY UNHARDENED GELATINVEHICLE AN IMAGE CORRESPONDING TO SAID SUBJECT PRESSING AN ABSORBENTSUPPORT AGAINST SAID LAYER WHILE SAID LAYER IS MOIST TO CAUSE SAID LAYERTO ADHERE TO THE SUPPORT AND WITHOUT DRYING SEPARATING SAID SUPPORT ANDLAYER TO TRANSFER A CONTINUOUS STRATUM OF THE ENTIRE LAYER TO SAIDSUPPORT.